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"The Staircase Implementation" is the twenty-second and penultimate episode of the third season of the American sitcom The Big Bang Theory. This episode first aired on Monday, May 17, 2010.


Leonard tells Penny the story of how he met Sheldon, Raj and Howard and what happened to break their elevator.

Extended Plot[]

Penny is about to do her toenails because she has her father's feet, when she hears Sheldon and Leonard fighting over the thermostat setting. Leonard comes over to Penny's apartment and asks if he can sleep on her couch. When Penny remarks that Leonard is nuts for living with Sheldon, he tells Penny the story of how he first met him seven years ago when Sheldon was worse.

Leonard starts out with explaining how, back in 2003, he had just started at Caltech and he needed a room for rent. The elevator was still working in the apartment building and he sees Sheldon's previous roommate, Sebastian, leaving and warning him about Sheldon being crazy. He does not heed this warning, thinking the previous roommate was the crazy one. After Leonard mistakenly knocks on his future transvestite neighbor's apartment door by mistake (who also considers Sheldon to be the crazy one), he eventually meets Sheldon. Sheldon first quizzes Leonard about his job and his science fiction character preferences before he allows him to enter. At this point, Sheldon's apartment is far more empty, having only two lawn chairs instead of the couch and armchair, although the lawn chair Sheldon sits on is in almost the same position as his present-day "spot"; the TV is balanced on cinder blocks. Sheldon gives a series of interview questions to verify whether or not Leonard is a good and worthy roommate to have and then gives him a tour, which includes showing him his future room with the message "DIE SHELDON DIE" painted on a wall by the previous roommate, which Sheldon says that Leonard might want to repaint. After working out seemingly countless pages of the roommate agreement, Leonard moves in.

Roommate agreement

Leonard signing the Roommate Agreement.

Penny cannot understand how Leonard decided to stay with Sheldon, and has no sympathy for him, following which Leonard tells her about when Sheldon kicked Joyce Kim, Leonard's new girlfriend, out of the apartment. This incident shocks Penny, and she asks why he still stayed after that. Leonard tells her it turned out to be a good thing as Kim was a North Korean spy and Leonard had been working on classified rocket fuel for the government: Joyce Kim was trying to seduce Leonard for information, which, due to Sheldon, proved unsuccessful as she then defected back to North Korea. Penny now knows half of the story now: Leonard stayed with Sheldon because the latter protected him from going to prison for treason.

Joyce Kim

Leonard in bed with Joyce Kim.

Leonard mentions that the other part of his story has to do with the elevator's destruction, and he continues the story. Sheldon comes home from work and he meets Raj and Howard who work at the university too, for the first time; they and Leonard are playing a video game. Sheldon finds that Leonard has replaced Sheldon's lawn chairs with the sofa that is currently in the apartment, which Sheldon isn't too happy with initially. Soon, after a lot of switching spots, Sheldon finally claims his "spot" on the couch. After the other guys leave due to Sheldon's annoyances, they go to Howard's place. Sheldon then sits in his spot and joyously say, "Oh, yes!"


Leonard prepares to mix the rocket fuel into Tovex in order to create a combustible gel.

Leonard discovers that Howard has a rocket, which he claims could break the sound barrier if it was running on the fuel Leonard was working on. Leonard tells Penny that he had some rocket fuel in the apartment (which he was going to show to Joyce Kim) and they went back to mix some; however, Sheldon notices that Leonard did not adjust the fuel for Howard's rocket size correctly, and the fuel starts smoking, causing Leonard to panic. Leonard attempts to take it outside and confine the smoking fuel to the elevator, but Sheldon knows precisely how long he has until it explodes, so he pushes Leonard out of the elevator before stepping out himself and closing the door. Within seconds, the fuel explodes, explaining why the elevator no longer works. Leonard explains his continued friendship with Sheldon by pointing out that Sheldon saved his life and he didn't say anything to the landlord, the police, or Homeland Security.

While Penny gets a little annoyed at the fact that he is the reason that she has to use the stairs every day, Leonard asks her what she was doing seven years ago. While she lies to him about doing community service and studying hard, it is revealed to the audience that she was relieved holding a negative pregnancy test.

Leonard goes back to the apartment and apologizes to Sheldon for his argument over the thermostat; however, when Leonard turns the TV on and tries to watch Babylon 5, a whole new fight starts, greatly amusing Penny.



  • "A terrific episode. It wasn't as emotionally resonant or as funny as it might have been but I have no complaints with a real good faith effort to apply actual characterization to these characters...First off I was delighted to see a flashback story; just to see The Big Bang Theory try something new was good. But the flashback is always a rich source for sitcoms and this was no exception...This isn't the show's best episode by any means. But it's one that does such a good job with continuity, characterization and just changing the formula that it encourages me as a viewer to invest more in future episodes. Great work." - The TV Critic's Review
  • IMDb user reviews


  • Title Reference: After a failed experiment renders the elevator useless, the staircase has to be used (and is therefore often featured as a setting for conversations between various characters).
  • Chuck Lorre's vanity card [1]
  • This episode was watched by 15.02 million people with a rating of 5.5 (adults 18–49).
  • This episode aired in Canada on May 17, 2010, with 2.72 million viewers and a weekly ranking of #2.
  • Episode transcript [2]

Costume Notes[]

Flash on black UnknownFlying Cross Hawkman


  • The hitherto unseen characters of Joyce Kim, a North Korean spy who dated Leonard, and the pair's original neighbor, Louie/Louise, the "200 pound transvestite with a skin condition" are seen.
  • In "The Hot Tub Contamination" (S10E05), Sheldon states that he knocks three times on the door due to once catching his father having an "affair". This is contradictory to the story in this episode, in which Sheldon tries to enter the room while Leonard is in bed with Joyce Kim. They try to ignore Sheldon's knocking, but he says he will knock until Leonard lets him in. It takes three knocks for Leonard to ask Sheldon what he wants, which Sheldon takes as a cue to enter.
  • Sheldon's lawn chair faced the television at a direct angle, thus discouraging conversation. As explained in the "pilot" (S1E1) and "The Gorilla Experiment" (S3E10), his spot faces the television at an indirect angle, thus encouraging conversation. (Apparently over the years he learned to tolerate company.)
  • During the second of three sets of questions, Sheldon asks if Leonard has a vehicle. Leonard has a car, but asks, "Can't you drive?" And Sheldon claims that "I can. I choose not to." During his simulated driving lessons he actually proved to be a very bad driver in "The Euclid Alternative" (S2E5); however, his face slightly twitches as he says it, which is one of Sheldon's facial tics that indicates he is lying.

Sheldon finds his spot.

  • Sheldon makes two blatantly wrong predictions in flashbacks: Firefly would run "for years" and told Raj that he would be sorry he wasted his money on an Apple iPod when Microsoft "comes out with theirs" (implying the Microsoft Zune would be more popular than the iPod series). Sheldon related the Zune story to Amy in "The Indecision Amalgamation" (S7E19). In reality, "Firefly" only lasted for one season before being cancelled by the Fox network because of low number of viewers due to episodes being shown out of order (leading to Sheldon's hatred towards Fox and, by extension, Rupert Murdoch) while the Microsoft Zune dwindled in sales from the moment it was released (with the entire line being discontinued a mere five years later after initial release), while the iPod became a global icon when it came to music players.
  • In Howard's room of 2003 they showed a Roboreptile toy and a slimline PS2, which came out the next year (it is possible he got them from testing them since he has a master's degree in mechanical engineering).
  • While forming the Roommate Agreement Sheldon finishes the section for television and movies and moves onto section 9: miscellanea, making television and movies section 8; however, in the flashback with Joyce Kim in Leonard's bedroom, Sheldon states that section 8 is visitors (most likely, section 8 was for both).
  • When Leonard, Howard, and Raj are playing on Sheldon's Nintendo Gamecube, you can closely hear the Waluigi Stadium/Wario Colosseum music from Mario Kart: Double Dash.
  • The Leonard in 2010 refers to events seven years ago (2003) and states, "I’d just started at the university." The past Leonard introduces Howard and Raj to Sheldon with, "They work at the university, too." These allusions to such an early point in time at the university, perhaps unintentionally, imply some of the main characters are not faculty members in the flashback. Since Leonard was born around 1980 (S4E10:"The Alien Parasite Hypothesis"), and got his doctorate at twenty-four (S1E9:"The Cooper-Hofstadter Polarization"), he was not finished with graduate school when he started at Caltech. Similarly, Raj was born around 1981 (S1E8:"The Grasshopper Experiment"), which means at twenty-one or twenty-two years old, he probably wasn't finished with graduate school either. Howard, also born in 1981 (S2E1:"The Bad Fish Paradigm"), only has a master's degree, thus, the chronological events presented may not be a continuity concern regarding his character. Note this possible mistake has no bearing on child prodigy Sheldon, though. Further, Leonard must have completed his doctoral studies at Caltech, working as a graduate research assistant, and the same can likely be said of Raj.

    The gang in their early days.

  • Although the episode "The Nerdvana Annihilation" (S1E14), Season 1, in 2008, Leonard claims that the elevator has been broken for two years (2006). This episode states that the elevator has been broken since 2003.
  • In "The Jerusalem Duality" (S1E12): Penny: "I don’t understand, exactly how did he get any friends in the first place?" Howard: "We liked Leonard." The episode of this article clearly establishes that.
  • Sheldon gets upset when someone phrases a response with an air of uncertainty, as when he asks Leonard about the sixth noble gas. This act is also evident in "The Dead Hooker Juxtaposition" (S2E19), when Alicia pondered "freakishly feline."
  • Sheldon says to Leonard, as he introduces his room, "Huzzah!" He previously said it while discussing fifteenth century historical inaccuracies at the Renaissance Fair in "The Codpiece Topology" (S2E22).
  • Sheldon put Leonard in his spam folder after he forwarded him a picture of a cat playing the piano, entitled "This is Funny." In "The Panty Piñata Polarization" (S2E7), Sheldon told Penny she violated his rule about forwarding email humor, the photo of the cat who wants to “has cheezburger," and gave her a "strike." Sheldon considers LOLcats Internet banality.
  • One of Leonard's whiteboards contains an analysis of hydrazine propulsion systems, specifically, the chemical equation for the irreversible process spontaneous exothermic chemical decomposition of hydrazine, followed by an equation for the endothermic dissociation of ammonia into hydrogen and nitrogen. Referenced thrust values, including those for the Space Shuttle Main Engine (SSME) and Saturn-V, are also provided. Sheldon's work on his whiteboards is on Ginzburg-Landau Theory.
  • Even if Sheldon or Leonard invented time travel at some point in the future, it would be impossible for them to go back and give it to themselves, as this would create a predestination paradox. One would expect Sheldon to understand this though he believes that time travel is on a closed loop as stated in "The Bow Tie Asymmetry".
  • Sheldon's old mobile phone is a Palm Treo.
  • On iTunes, the date of the flashbacks is Apr. 28, 2003.
  • This is the second episode where Sheldon claims he is in hell due to mundane discomfort, following "The Gorilla Experiment" (S3E10).
  • Sheldon gets angry about Leonard setting the thermostat to 73 degrees. Ironically, 73 is his favorite number.
  • This is the first episode where Penny's family home in Nebraska is shown, where we see here what is obviously her old bedroom.
  • This episode takes place in 2003 and could also be watched chronologically before the pilot episode. It could also be watched as a fantasy retrospective. This is similar to Star Trek episode "The Menagerie", which recycled footage from the original Star Trek pilot "The Cage".
  • The present day Howard and Raj do not appear in this episode.
    • Also, the present day Sheldon does not make a physical appearance until the last scene of the episode.
  • The elevator becomes inoperative in 2003 and would not become operational again for another 16 years (in the series' penultimate episode, "The Change Constant").


  • Sheldon intrudes upon Leonard while he is in bed with Joyce Kim. In "The Hamburger Postulate", when Leonard and Leslie Winkle are having sex, Sheldon is unsure of what to do in those kind of situations, and states that it has never happened before. He asks Penny for advice. In this episode, he breaks into Leonard's room right when Leonard and Joyce Kim are making out, contradicting Sheldon's statement in "The Hamburger Postulate".
    • However, Leonard and Joyce weren't technically having coitus at the time.
    • His tentativeness with the situation with Leslie was due to the loud music and tie on the door knob, so these 2 events aren't supposed to be related.
  • When Sheldon says, “The second barrier. Don‘t get cocky.“, the closed captioning says, “Don‘t get coy.‘‘


(Penny is about to do her nails)
Penny: Okay, Babydoll Pink, let's see if you can cover up the fact that I got my dad's feet.
(Leonard and Sheldon have started fighting which can be heard from Penny's place)
Leonard: 2 degrees, Sheldon! I just wanna turn up the thermostat by 2 degrees!
Sheldon: Let me point out that 2 degrees can be the difference between water and steam!
Leonard: Yes, if we lived in a tea kettle!
Sheldon: This is the temperature you agreed to in the Roommate Agreement!
Leonard: Aw, screw the Roommate Agreement!
Sheldon: No, you don't screw the Roommate Agreement, the Roommate Agreement screws you!
Leonard: You know what, Go to hell and set their thermostat!
Sheldon: I don't have to go to hell. At 73 degrees, I'm there (at the apartment) already!
(Leonard slams their door and knocks on Penny's.)
Penny: Who is it?
Leonard: Leonard.
Penny: Hang on.
(She walks on her heels to get to the door so she doesn't ruin her nail job.)
Leonard: Can I sleep on your couch tonight?
Penny: Uh, well, you can try, but the people across the hall are being very noisy.
Leonard: You heard that, huh?
Penny: Apparently, the one fella tried to adjust the thermostat, then the other fella went bat-crap crazy.
Leonard: So you agree, he's nuts!
Penny: Well, not as nuts as the guy who chooses to live with him.
Leonard: Believe it or not, he was worse when I met him.
Penny: (Naively chuckles) Oh, I do not believe that.
Leonard: You are so naive. Just like I was seven years ago.
(Leonard starts telling the story of how he met Sheldon.)
Leonard: "I just started at the university."
(It is the year 2003 and we see that when Leonard was younger, he originally had a "classic" Weird Al hairstyle, and tortoiseshell glasses. He then sees Sheldon's previous roommate leaving the elevator, which was still operational at the time.)
Leonard: Hi, excuse me, I'm looking for Sheldon Cooper's apartment?
Ex-Roommate: Oh, I bet you're here to check out the room for rent.
Leonard: Yeah.
Ex-Roommate: Run away, dude!
Leonard: What?
Ex-Roommate: Run fast, run far!
(Back in 2010)
Leonard: That should have been my first clue.

Leonard: (voiceover) Anyway, I went upstairs and knocked on the door.
(2003 Leonard comes out of the elevator, walks over to 4B's apartment and knocks. The door opens and he is confronted by a large muscular African-American man with breasts and dressed as a woman)
Louie/Louise: (curtly) Yeah?
(Long pause, as Leonard is speechless. Louie gives him an impatient look)
Leonard: (confusedly) Dr. Cooper?
Louie/Louise: Nah, you want the crazy guy across the hall. (steps back into his apartment and closes the door)
Leonard: (voiceover, as his past self crosses over to Sheldon's front door) In retrospect, that was clue number 2.

Sheldon: What is the sixth noble gas?
Leonard: What?
Sheldon: You said you're a scientist. What is the sixth noble gas?
Leonard: Uh, radon?
Sheldon: Are you asking me or telling me?
Leonard: Telling you?
(Sheldon gives Leonard an impatiently angry look)
Leonard: Telling you.
Sheldon: All right. Next question. Kirk or Picard?
Leonard: Oh, uh, well, that's tricky. Um, Original Series over Next Generation, but Picard over Kirk.
Sheldon: Correct. You've passed the first barrier to room-mate-hood. You may enter.

(Leonard is about to sit in a lawn chair, approximate to where Sheldon's spot is in the present.)
Sheldon: No, that's where I sit!
Leonard: What's the difference?
Sheldon: This seat is ideally located, both in relation to the heat source in the winter and a cross breeze in the summer. It also faces the television at a direct angle, allowing me to immerse myself in entertainment or game play, without being subjected to conversation. As a result, I've placed it in a state of eternal dibs.
Leonard: Can you do that?
Sheldon: Cathedra mea, regula maea. That's Latin for "my chair, my rules".

(Sheldon is busy getting Leonard to sign the roommate agreement )
Sheldon: Roommates agree that Friday nights shall be reserved for watching Joss Whedon's brilliant new series, "Firefly".
Leonard: Does that really need to be in the agreement?
Sheldon: Well we might as well settle it now, it's gonna be on for years.

Sheldon: Mmm, I assure you, you'll be sorry you wasted your money on an iPod, when Microsoft comes out with theirs.
Raj: OK, do you have an opinion about everything?
Sheldon: Yes.
Howard: You just assume you're always right?
Sheldon: It's not an assumption.

Leonard: Oh, it's time for Babylon 5.
Sheldon: But we don't watch Babylon 5 in this apartment.
Leonard: Why not?
Sheldon: Because no one likes Babylon 5.
Leonard: Well, I like it.
Raj: Me too.
Howard: So do I.
Leonard: There you go, 3 against 1.
Sheldon: They don't get a vote. It's 1 against 1 and according to the roommate agreement; all ties will be settled by me.
Leonard: But I said no to that.
Sheldon: And I said yes. And I settle all ties.

(In 2003: Leonard, Raj and Howard are at Howard's House, not Sheldon's Apartment)
Mrs. Wolowitz (shouting downstairs in the hall.): HOWAAAHD, ARE YOU HAVING A PLAYDATE?!
Howard (with Curly Hair): (also shouting back): DON'T HAVE PLAYDATES, I HAVE COLLEAGUES!
Leonard: Is that your dad?
Howard: If she grows any more hair on her face, yes.

Howard: I HAVEN'T SEEN YOUR OREOS, (Doesn't notice that Raj is eating them) JUST TAKE YOUR BATH WITHOUT THEM!

(Leonard has just told Penny that Howard had a model rocket and only needed some of the fuel that Leonard was making for the government to get it going)
Penny: So why was it his lucky day?
Leonard: Well, it turns out I had a little rocket fuel in the apartment.
Penny: What were you doing with a rocket fuel in your apartment?
Leonard: Well, Joyce Kim was kind of curious about what I did for a living, and I was gonna, it to her. It's not important, the point is the guys and I went back to the apartment.
Penny: OK, but are we ever going to get to the elevator?
Leonard: Yeah, we're really close; we're at the apartment....
(In 2003: Leonard is mixing rocket fuel for Howard's model rocket; however, it is incorrect, though nobody yet knows this.)
Leonard: The trick is to mix it in a Tovex in order to create a combustible gel that will generate over eight thousand kilonewtons of thrust.
(Howard and Raj excitedly chuckle)
Raj: Cool!
Sheldon: Won't work.
Leonard: Excuse me, but I've been working on this a long time. Trust me, it will work.
Sheldon: You don't see your mistake, do you?
Leonard: There's no mistake.
Sheldon: This is for a full scale rocket, not a model.
Leonard: Well I've adjusted the formula.
Sheldon: Not correctly.
Leonard: OK, I've had it with you! You might be an expert on theoretical physics, and science-fiction programs, and where to sit on a freaking couch! But this is "applied" physics, and when it comes to applied physics.... (the rocket fuel starts sizzling and he realises what's happened) ..... Ahh, uh-oh.
Howard: What's happening?!
Leonard: A bad thing, a very bad thing. Get the door! Get the door! Get the door! Get the door! Get the door!
(Sheldon turns their apartment's flag upside down, while the other 3 go out into the hallway where Leonard waits for the elevator.)
Howard: You're waiting for the elevator?!
Leonard: Oh, right!
(Leonard starts to go down the stairs, when the elevator arrives.)
Raj: Wait, its here!
Leonard: Ahhhhhhh! (Goes back up and into the elevator. As the door closes, Sheldon barges past Raj at an unusually quick pace, pushes the elevator doors back open and takes the rocket fuel out of his hands.)
Sheldon: Give me that! (Pushes Leonard out, presses the down button and exits the elevator. The doors close.
Leonard: What did you do that for?! I had plenty of ti-!
(There is a sudden, very loud explosion in the elevator, destroying it. All of them, except Sheldon are in shock and horror.)
Sheldon: You're welcome. (Sheldon goes back inside, with Leonard still dazed.)
(In 2010)
Leonard: Not only did Sheldon save my life, he didn't rat me out to the landlord. Or the police. Or Homeland Security.
Penny: Okay, so basically, you're the reason I have to walk up and down 3 flights of stairs every day?
Leonard: So, I did something stupid, I'm sure you did stupid things when you were younger; what were you doing 7 years ago?
Penny: Excuse me. I was in high school, studying, keeping my nose clean, doing volunteer work for the community...
(Cut to 2003, a teenage Penny, sporting Britney Spears-style hair, is back in Nebraska with a boyfriend, doing a pregnancy test.)
Penny: Not pregnant. Yes! (High-fives boyfriend.) Ha ha!

Sheldon: Oh, yes, this is definitely going to be my spot.